1. Field of the Invention
Embodiments of the invention generally relate to the field of semiconductor manufacturing processes and devices, more particular, to methods of implanting ions into a substrate by a plasma immersion ion implantation process.
2. Description of the Related Art
Integrated circuits may include more than one million micro-electronic field effect transistors (e.g., complementary metal-oxide-semiconductor (CMOS) field effect transistors) that are formed on a substrate (e.g., semiconductor wafer) and cooperate to perform various functions within the circuit. A CMOS transistor comprises a gate structure disposed between source and drain regions that are formed in the substrate. The gate structure generally comprises a gate electrode and a gate dielectric layer. The gate electrode is disposed over the gate dielectric layer to control a flow of charge carriers in a channel region formed between the drain and source regions beneath the gate dielectric layer.
An ion implantation process is typically utilized to implant, or dope, ions into the substrate, forming the gate and source drain structure with desired profile and concentration on the substrate. During an ion implantation process, different process gases or gas mixtures may be used to provide ion source species. As the process gases are supplied into the ion implantation processing chamber (such as a P3i chamber commercially available from Applied Materials, Inc., of Santa Clara, Calif.), the gases are subjected to processes to dissociate ions, which are then accelerated toward and into the surface of the substrate. As ions accelerated to the substrate surface are typically in a linear movement, e.g., one directional movement, the ions are mostly implanted into a bottom surface of a structure, e.g., patterns or trenches, formed on the substrate surface rather than to sidewalls of the structure. Non-conformal ion doping may result in insufficient and/or non-uniform ion concentration, profile, dimension, and distribution across the substrate surface, especially in feature definitions formed in the substrate surface, thereby adversely affecting the overall electrical device performance. As critical dimensions shrink, the precision of ion implantation becomes increasingly important.
Therefore, there is a need for an improved ion implantation process to provide for a more conformal implantation of ions on a substrate surface and in feature definitions.